ITE Letters 8 (6): 708-712 (2007).
ITE Letters on Batteries, New Technologies & Medicine, Vol. 8, No.3 (2007) Lack of Correlation between the Rates of Local Industrial and Household Energy Consumptions and the Seasonal Outbreaks of Tropospheric Photochemical Oxidants in Two Japanese Cities Ken YOKAWA and Tomonori KAWANO* Graduate School of Environmental Engineering, The University of Kitakyushu, Wakamatsu-ku, Kitakyushu 808-0135, Japan *Correspondence: T.K. (e-mail:
[email protected]); FAX +81-93-695-3304 Received Nov. XX, 2007; accepted for publication Nov. XX, 2007
ABSTRACT Current data suggest that the atmospheric levels of photochemical oxidants in Japanese cities are increasing year by year. By law, local governments in Japan such as those of prefectures and some big cities are supposed to issue the photochemical smog alerts based on the on-site real-time monitoring of photochemical oxidant levels if exceeding over 0.12 ppm/h. Upon the alert issued, industrial energy consumption control in the corresponding cities is enforced, again by law, in order to cut down the emission of any chemicals behaving as the precursors of photochemical oxidants. The purpose of this study is to re-evaluate the significance of such on-site control of energy consumption restricting the industrial operations for minimizing the level of seasonally produced photochemical oxidants. By assessing the seasonal changes in the levels of photochemical oxidants and local energy consumption, we discussed the effectiveness of the law-defined local actions against the current problems. KEYWORDS: Air pollution; Long-range transport, Ozone ; Photochemical oxidant
INTRODUCTION Photochemical oxidants (ozone as the major component) are secondary pollutants generated through photochemical reactions. In the atmosphere, ultraviolet (UV) rays stimulates the reactions among the primary air pollutants such as nitrogen oxides (NOx) and/or hydrocarbons (HCs) emitted from the industries and electric power plants, leading to generation of secondary pollutants [1-3]. Secondary pollutants such as ozone and peroxyacetyl nitrate (PAN) are referred to as the photochemical oxidants while their real-time monitoring is likely based only on the detection of
ozone. Atmospheric ozone not only directly stimulates the mucous membranes such as respiratory organs in human [4] but also damages living plants [3] and plant cells [5]. In May 2007, the presence of notably high concentration of photochemical oxidants represented by ozone was recorded in all over Japan. As a consequence, number of cities (including Kitakyushu city) issued official warning for the first time in recent 10 years as the atmospheric concentration of photochemical oxidants (determined as ozone) attained the law-defined alert level (0.12ppm/h, continuous air pollution monitoring system). Simultaneously, the local
governments announced for voluntary restraint actions to the residents through broadcasting or using loudspeaker vans, asking people not to go out (even by cars) not to leave windows open. Computational simulation conducted by a Japanese team suggested that the waves of photochemical oxidants were brought from the continent (i.e. from Chinese coasts through Korea to Japan; T. Ohara, Press-release from National Institute for Environmental Studies, May 21st, 2007, http://www.nies.go.jp/ whatsnew/2007/20070521/20070521.html), suggesting that the concentrations of the “cross-border ozone” exceeded the level defined in the warning guidelines in Japan as predicted in the previous reports [6-10]. Once the alert is issued, immediate actions must be made in the industries as defined by a national law; thus, more than 20% of NOx emission from industrial factories and facilities are proposed to be cut-off by reducing the consumption of fuel, burning of materials and operation of facilities. The actions defined originally aimed to lower the levels of photochemical
Fig. 1.
oxidants by reducing emission of the key precursors, NOx, from the factories nearby the sites of air pollution. In this study, we attempted to challenge the widely accepted view or belief that the recent increases in local photochemical oxidant levels are still due to the local industrial activities, by showing the lack of significant correlation between the local industrial energy consumption rates (reflecting the industrial activities) and the local photochemical oxidant levels. The results were in support of the opposing view that photochemical oxidants and their precursors were generated in the oversea or distant regions and brought to Japan since the local industrial activities measured with energy consumption rates showed no contribution to the seasonal changes in photochemical oxidant levels. Therefore, significance of the law-defined action forcing the local industrial energy consumption control must be reconsidered and possible alternative approaches to lower or to minimize the long-range transport of air pollutants must be urgently taken.
Changes in annual mean photochemical levels in Kitakyushu and Tokyo in recent 3 decades. (a) Map of the
East-Asia. Arrows indicates the locations of Kitakyushu and Tokyo. (b, c) Transition of atmospheric oxidant levels between 1976 and 2005 in two cities. (d) Current increases in oxidant levels in two cities.
Fig. 2. Seasonal changes in atmospheric oxidant levels recorded in two cities. (a) Kitakyushu, (b) Tokyo.
SOURCES OF DATA Data for local photochemical oxidant levels in Tokyo (at Chiyoda observatory station) and Kitakyushu (at Moji observatory station) were obtained from Atmospheric Environmental Regional Observation System (AEROS), run by the Ministry of the Environment (http://soramame.taiki.go.jp/). Data for annual and monthly mean consumption of electricity in specific regions were obtained from an open source (http://www.fepc.or.jp/) and the statistics of fuel consumption was obtained from database of Ministry of Economy, trade and industry
(http://www.meti.go.jp/statistics/).
RESULTS AND DISCUSSION Figure 1 shows the changes in atmospheric photochemical oxidant levels within recent 3 decades recorded in Kitakyushu and Tokyo. Before the 1980s, severe air pollutions with high level of oxidants accompanying the economic burst in the country were recorded both in Kitakyushu and Tokyo. After the peaks, sharp declines in annual photochemical oxidant level were achieved (Fig. 1b,c) as Japanese government had issued a series of air quality-related laws. However,
Fig. 3. Seasonal transition of energy (electricity) consumption rates in Tokyo and Fukuoka. Domestic (house-hold) energy consumptions (a, c) and industrial energy consumptions (b, d) in Fukuoka prefecture where Kitakyushu city locates within (a, b), and Tokyo (c, d) are compared. The categories in (b) and (d) include fiber/textile, paper/pulp, ceramics, steels, nonferrous metals, machines, and other industries.
the trends of the annual changes in atmospheric ozone levels in recent 15 years suggest that the background ozone levels are increasing (Fig. 1d). This is consistent with the world trends of background ozone levels in which the annual mean ozone levels have been doubled in the past one hundred years and expected to be further doubled in the coming century [3]. In Kitakyushu (Fig. 2a), the tendency of seasonal variations in atmospheric oxidant levels shows two distinct peaks around May and October. On the other hand, only a single but broaden peak appears in summer in Tokyo (Fig. 2b). Seasonal changes in electricity consumption rates in Kitakyushu and Tokyo showed that domestic (house-hold) energy consumption rates in both cities are largely elevated in every summer season examined (2003-2005), possibly because of the elevated needs for air conditioning and other cooling apparatuses (Fig. 3a,c). On the other hands, the seasonal changes in industrial energy consumption rates were less obvious, but the trends showed that the industrial energy demands are higher in summer (June to September) and lower in the mid winter (January and February).
To clarify whether the recent increases in photochemical oxidants were due to local industrial energy utilization or not, we assessed the relationships between the trends of local energy consumption and the levels of photochemical oxidants using the recent data (2003-2005). From such analyses, no significant correlation or relationship was elucidated with any combination of the data (i.e. monthly mean oxidant levels recorded in two cities versus monthly mean values of house-hold or industrial energy demands recorded either in Tokyo or Fukuoka prefecture where Kitakyushu is surrounded; Fig. 4a-d). These analyses uncovered the disconformities in the widely accepted belief that seasonal variations in photochemical oxidants in western and central Japan are due to the emission of the oxidant precursors from the local sources within Japanese cities and surrounded area.
PERSPECTIVE
Fig. 4. Lack of correlation between the levels of atmospheric photochemical oxidants and local energy (electricity) consumption rates. Relationships between monthly mean oxidant levels and the domestic (house-hold) energy consumptions (a, c) and industrial energy consumptions (b, d) in Fukuoka prefecture (Kitakyushu; a, b), and Tokyo (c, d) were assessed.
Table.1. Seasonal changes in gasoline consumption in Japan (Tokyo????) recorded in 2006.
Month Consumption
Jan.
Feb.
Mar.
Apr.
May
Jun.
Jul.
Aug.
Sep.
Oct.
Nov.
Dec.
5.06
4.48
5.02
4.65
4.56
4.43
4.90
5.47
4.72
4.76
4.84
5.15
Unit, Mega tons.
In this work, we examined the relationship between the photochemical oxidant levels and electricity consumption levels in two Japanese cities, and found that contribution of local energy consumptions are not contributing to seasonal spikes in photochemical oxidant. Thus, we concluded that industrial energy consumption control (largely traceable by monitoring the changes in electricity consumption) defined by law must be reconsidered. However, the means of transportations such as vehicles, vessels and aircrafts are also greater sources of NOx which behave as the chemical precursors of ozone under strong sunlight. Therefore additional survey on the correlation between seasonal changes in transportation oxidant levels must be carried out. For instance, seasonal changes in the fuel consumption rate such as that of gasoline can be good measures of vehicle uses. We are quite optimistic about the further survey since the preliminary data reflecting the changes in traffic density likely lack the correlation with the seasonal changes in photochemical oxidants. Table 1 shows the seasonal changes in national (OR Tokyo????) gasoline consumption rates. The trends found in this sort of data are obviously opposing to the trends in seasonal photochemical oxidant outbreaks. Such preliminary data on fuel consumption are also in support of the view that photochemical oxidants and their precursors might have been brought from the oversea sources as the recent computational simulations implied.
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Ken Yokawa, Graduate student of graduate school of Information, Production & Systems, Waseda University. Areas: Computational cell biology, Biochemistry.
